Haemorheological use of N-alkylated 1,4-dihydropyridine-dicarboxylic acid esters, and some new compounds

ABSTRACT

Improving circulation, with minimal effect on blood pressure, using N-alkylated 1,4-dihydropyridines of the formula ##STR1## in which R 1  represents hydrogen, nitro, cyano, trifluoromethyl, trifluoromethoxy, halogen or methyl, 
     R 2  represents hydrogen, halogen, nitro, hydroxyl, trifluoromethyl or methyl, 
     R 3  represents hydrogen or cyano, or 
     R 2  and R 3  together form a fused benzo ring, 
     R 4  and R 5  are identical or different and represent straight-chain or branched alkyl having up to 8 carbon atoms, which is optionally substituted by alkoxy having up to 4 carbon atoms, and 
     R 6  represents straight-chain or branched alkyl having up to 10 carbon atoms or represents cycloalkyl having 3 to 7 carbon atoms. 
     Many of the compounds are new.

This is a division of application Ser. No. 07/680,454, filed Apr. 4, 1991, now U.S. Pat. No. 5,236,935.

The present invention relates to the use of N-alkylated 1,4-dihydropyridinedicarboxylic acid esters, some of which are known, as haemorheological medicaments, new active compounds and processes for their preparation, in particular their use as medicaments in acute and chronic ischaemic disorders which are associated with microcirculation disorders. This action can occur both in the peripheral and in the cerebral vascular system.

It is known that 1,4-dihydropyridinedicarboxylic acid esters have a calcium antagonist or calcium agonist action, and can thus be employed as circulation-influencing agents [compare DOS (German Offenlegungsschrift) 2,506,987; DE 2,210,667].

EP 240,828 describes hypotensive 1,4-dihydropyridines having haemorheological properties.

The use of hypotensive 1,4-dihydropyridines substituted by heterocycles as haemorheological agents has also been published in DE 3,720,509.

It has now been found that the N-alkylated 1,4-dihydropyridinedicarboxylic acid esters, some of which are known and some of which are new, of the general formula (I) ##STR2## in which R¹ represents hydrogen, nitro, cyano, trifluoromethyl, trifluoromethoxy, halogen or methyl,

R² represents hydrogen, halogen, nitro, hydroxyl, trifluoromethyl or methyl,

R³ represents hydrogen or cyano, or

R² and R³ together form a fused benzo ring,

R⁴ and R⁵ are identical or different and represent straight-chain or branched alkyl having up to 8 carbon atoms, which is optionally substituted by alkoxy having up to 4 carbon atoms, and

R⁶ represents straight-chain or branched alkyl having up to 10 carbon atoms or represents cycloalkyl having 3 to 7 carbon atoms,

surprisingly have a strong haemorheological action combined with neutral blood pressure behavior and improve the circulation, in particular the microcirculation, and are thus suitable for use in the control of acute and chronic ischaemic disorders.

Compounds of the general formula (I)

in which

R¹ represents hydrogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, fluorine, chlorine, bromine or methyl,

R² represents hydrogen, fluorine, chlorine, bromine, nitro, hydroxyl, trifluoromethyl or methyl,

R³ represents hydrogen or cyano, or

R² and R³ together form a fused benzo ring,

R⁴ and R⁵ are identical or different and represent straight-chain or branched alkyl having up to 8 carbon atoms, which is optionally substituted by methoxy and

R⁶ represents straight-chain or branched alkyl having up to 4 carbon atoms, or cyclopropyl,

are preferred for the control of acute and chronic ischaemic disorders.

Compounds of the general formula (I)

in which

R¹ represents hydrogen, nitro, trifluoromethyl, trifluoromethoxy, cyano, fluorine, bromine, chlorine or methyl,

R² represents hydrogen, fluorine, chlorine, nitro, hydroxyl, trifluoromethyl or methyl,

R³ represents hydrogen or cyano, or

R² and R³ together form a fused benzo ring,

R⁴ and R⁵ are identical or different and represent straight-chain or branched alkyl having up to 6 carbon atoms, which is optionally substituted by methoxy, and

R⁶ represents methyl, ethyl or cyclopropyl, are particularly preferred for the control of acute and chronic ischaemic disorders.

The compounds according to the invention show an unforeseeable, useful pharmacological action spectrum.

Combined with a neutral blood pressure behavior in a dose range up to at least 10 mg/kg i.v. and 30 mg/kg p.o., they increase the circulation, in particular the microcirculation, by influencing the deformability of erythrocytes and also the inhibition of the activation and adhesion of leukocytes.

The blood pressure neutrality is determined in the following models, which are typical for dihydropyridines: in SH rats after p.o. administration by measurement in the tail artery (Riva Rocci method) and in anaesthetized Wistar rats after i.v. administration (via a catheter inserted in the carotid artery). Blood-neutral compounds are designated as those which reduce the blood pressure by at most 20% of the starting value in both test models at the dose indicated. The difference between the therapeutic dose and the blood pressure action occurring is at least a factor of 10, as a rule a factor of ≧30, in particular ≧100.

They can therefore be employed for the production of medicaments for the treatment of acute and chronic ischaemic disorders, such as intermittent claudication, myocardial infarct, cerebral infarct and also reperfusion damage and shock.

The invention additionally relates to new 1,4-dihydropyridinedicarboxylic acid esters which are listed below:

dibutyl 1,2,6-trimethyl-4-(1-naphthyl)-1,4-dihydropyridine-3,5-dicarboxylate

diethyl 1,2,6-trimethyl-4-(4-fluorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dipropyl 1,2,6-trimethyl-4-(2-cyanophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dibutyl 1,2,6-trimethyl-4-(4-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

methyl propyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

methyl isopropyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

methyl 1,2-dimethylpropyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

methyl 2-methoxyethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(3-fluorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dipropyl 1,2,6-trimethyl-4-(3-methylphenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(4-bromophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dipropyl 1,2,6-trimethyl-4-(4-bromophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dibutyl 1,2,6-trimethyl-4-(4-bromophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

dipropyl 1,2,6-trimethyl-4-(4-cyanophenyl)-1,4-dihydropyridine-3,5-dicarboxylate

diethyl 1-cyclopropyl-2,6-dimethyl-4-(3-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1-ethyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diisopropyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(4-methyl-3-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dipropyl 1,2,6-trimethyl-4-(4-methyl-3-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dibutyl 1,2,6-trimethyl-4-(4-methyl-3-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1,2,6-trimethyl-4-(4-methyl-3-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1,2,6-trimethyl-4-(3-chloro-4-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(4-chloro-3-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(4-methyl-3-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1,2,6-trimethyl-4-(3-hydroxy-4-nitrophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethoxyphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethoxyphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

isopropyl 2-methoxyethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

methyl ethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine- 3,5-dicarboxylate

propyl 2-methoxyethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

isopropyl 2-methoxyethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

diethyl 1-cyclopropyl-2,6-dimethyl-4-(4-fluorophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

dimethyl 1-cyclopropyl-2,6-dimethyl-4-(4-fluorophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

propyl butyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluorophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

butyl methyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

ethyl propyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

butyl ethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate

ethyl isopropyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate.

Particularly preferred compounds are the 1,4-dihydropyridinedicarboxylic acid esters whose phenyl ring is monosubstituted in the para-position by fluorine, bromine or by the CF₃ group.

Very particularly preferred compounds are the following:

dimethyl 1,2,6-trimethyl-4-(4-bromophenyl)-1,4-dihydropyridine-3,5-dicarboxylate (Ex 13)

diethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate (Ex 19)

dimethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate (Ex 18)

dimethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate (Ex 3)

methyl 1,2-dimethylpropyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate.

Some of the compounds according to the invention exist in stereoisomeric forms which behave either as image and mirror image (enantiomers) or which do not behave as image and mirror image (diastereomers). The invention relates both to the antipodes and to the racemic forms and the diastereomer mixtures. The racemic forms can be separated into the stereoisomerically uniform components in a known manner, just like the diastereomers (compare E. L. Eliel, Stereochemistry of Carbon Compounds, McGraw Hill, 1962).

The compounds of the general formula (I) according to the invention and the new compounds can be prepared by a process in which

[A] benzylidene compounds of the general formula (II) ##STR3## in which R^(1'), R^(2'), R^(3') and R^(4') have the abovementioned meaning of R¹, R², R³ and R⁴ and additionally include the respective scope of meaning of the new compounds listed above, are either first reacted with β-aminocrotonic acid esters of the general formula (III) ##STR4## in which R^(5') has the abovementioned meaning of R⁵ and additionally includes the scope of meaning of the new compounds listed above, in inert solvents and in a last step the NH function is alkylated by a customary method, or

the compounds of the general formula (II) are directly reacted, if desired in the presence of Lewis acids such as titanium tetrachloride, with compounds of the general formula (IIIa) ##STR5## in which R^(5') has the abovementioned meaning,

R^(6') has the abovementioned meaning of R⁶ and additionally includes the scope of meaning of the new compounds listed above, or

[B] aldehydes of the general formula (IV) ##STR6## in which R^(1'), R^(2') and R^(3') have the meanings indicated under process [A ], are first reacted with β-ketocarboxylic acid esters of the general formulae (V) and (Va) ##STR7## in which R^(4') and R^(5') likewise have the meanings indicated under process [A], and then are either reacted directly with amines or the corresponding amine hydrochlorides of the general formula ( VI )

    H.sub.2 N--R.sup.6'                                        (VI)

in which

R^(6') has the meaning indicated above under process [A] or

are first ring-closed with ammonia in organic, if appropriate inert, solvents according to a customary method and in a last step alkylated by the method mentioned above,

and in the case of the enantiomerically pure esters, the enantiomerically pure carboxylic acids are first prepared and these are esterified with the appropriate alcohols by a customary method, if desired by means of a reactive acid derivative.

The process, according to the invention, for the preparation of the new compounds can be illustrated by way of example by the following equation: ##STR8##

Description of Processes

Suitable solvents are water, or organic solvents which do not change under the reaction conditions. These preferably include alcohols such as methanol, ethanol, propanol, isopropanol, ethers such as diethyl ether, dioxane, tetrahydrofuran, glycol monomethyl ether or glycol dimethyl ether, or amides such as dimethylformamide, dimethylacetamide or hexamethylphosphoric triamide, or glacial acetic acid, dimethyl sulphoxide, acetonitrile or pyridine.

The reaction temperatures can be varied within a relatively wide range. In general, the reaction is carried out between +10° C. and +150° C., preferably between +20° C. and +100° C., in particular at the boiling point of the respective solvent.

The reaction can be carried out at normal pressure, but also at elevated or reduced pressure. In general, the reaction is carried out at normal pressure.

When carrying out process variants A and B according to the invention, any desired ratio of the substances participating in the reaction can be used. In general, however, molar amounts of the reactants are used. The isolation and purification of the substances according to the invention are preferably carried out by removing the solvent by distillation in vacuo and recrystallizing the residue, which may only be obtained in crystalline form after ice-cooling, from a suitable solvent. In some cases, it may be necessary to purify the compounds according to the invention by chromatography.

The ylidene compounds of the general formula (II) are known in some cases or can be prepared by known methods [compare H. Dornow and W. Sassenberg, Liebigs Ann. Chem. 602, 14 (1957)].

The aldehydes of the general formula (IV) employed as starting materials are known or can be prepared by known methods [DOS (German Offenlegungsschrift 2,165,260; 2,401,665; T. D. Harris, G. P. Roth, J. Org. Chem. 44, 2004 (1979); W. J. Dale, H. E. Hennis, J. Am. Chem. Soc. 7.8, 2543 (1956); Chem. Abstr. 59, 13929 (1963)].

The β-ketocarboxylic acid esters of the general formulae (V) and (Va) employed as starting materials are known or can be prepared by known methods [D. Borrmann in Houben Weyl's "Methoden der organischen Chemie" (Methods of Organic Chemistry) Vol. VII/4,230 (1968); Y. Oikawa, K. Sugano, O. Yonemitsu, J. Org. Chem. 43, 2087 (1978)].

The β-aminocrotonic acid esters of the general formulae (III) and (IIIa) employed as starting materials are known or can be prepared by known methods [DOS (German Offenlegungsschrift) 2,228,377; F. A. Glickman, A. C. Cope, J. Am. Chem. Soc. 67, 1017 (1945)].

The compounds of the general formula (VI) are also known.

Examples of reactive acid derivatives which may be mentioned are: activated esters, hydroxysuccinimide esters, acid imidazolides, acid halides, mixed anhydrides or reaction in the presence of cyclohexylcarbodiimide

Examples of alkylating agents which can be employed in the process are (C₁ -C₈)-alkyl halides, sulphonic acid esters or substituted or unsubstituted (C₁ -C₆)-dialkyl sulphates, preferably methyl iodide, p-toluenesulphonic acid esters or dimethyl sulphate.

The alkylation is carried out in the above-mentioned solvents at temperatures from 0° C. to +150° C., preferably at room temperature up to +100° C. at normal pressure.

Activating reagents which may be mentioned by way of example for the preparation of the reactive acid derivatives are, in addition to the inorganic halides such as thionyl chloride, phosphorus trichloride or phosphorus pentachloride, or carbonyldiimidazole, carbodiimides such as cyclohexylcarbodiimide or 1-cyclohexyl-3-[2-(N-methyl-morpholino)ethyl]carbodiimide-p-toluenesulphonate or N-hydroxyphthalimide or N-hydroxybenzotriazole in the presence of dicyclohexylcarbodiimide.

Suitable solvents for the reaction with the appropriate alcohols are the abovementioned solvents with the exception of the alcohols.

The diastereomer pairs are separated by known methods such as column chromatography, fractional crystallization or Craig partition [for Craig partition see, for example, "Verteilungsverfahren im Laboratorium" (Partition Methods in the Laboratory), E. Hecher, Verlag Chemie GmbH, Weinheim, Bergstr. (1955)].

The new and the known compounds according to the invention show an unforeseeable, useful pharmacological action spectrum.

The following in vitro and in vivo tests show the interesting actions of the compounds according to the invention.

I) Erythrocyte function

The deformability of erythrocytes plays an essential role in the origin and course of acute or chronic ischaemic disorders. It determines the viscosity of the blood and thus its distribution in the microcirculation. The tests used detect various determinants:

Test a) measures the calcium permeability (⁴⁵ Ca) by blockade of the ATPases by Na ortho-vanadate. As a result, calcium can accumulate in the erythrocytes. A consequence is a reduced flexibility. ED₅₀ values (mol/l) for the inhibition of calcium influx are given for test a).

Test b) detects the antihaemolytic action of the substances (ED₅₀, mol/l ). In this test, calcium-laden erythrocytes are forced through small pores under high shearing stresses, so that haemoglobin is released as a result of their haemolysis and measured. The reduction in haemoglobin release is the measured quantity.

Test c) detects the filterability of calcium-laden erythrocytes through 5 μm pores (ED₅₀, mol/l ). In this test, the membrane flexibility plays a role under small force gradients.

Test d) detects the viscosity of erythrocyte suspensions in glass capillaries (25 μm diameter) at low shearing stresses occurring in areas of vessels behind a stenosis. As a result of increasing the extracellular calcium, the viscosity increases.

The table gives the percentage improvement in the viscosity relative to damage=100% at a test dose of 10 ng/ml.

a) Calcium permeability of erythrocytes:

After blockade of the membrane-immobilized ATPases by Na ortho-vanadate (0.75 mM), the calcium permeability is measured (⁴⁵ Ca method). Accumulation of calcium reduces the flexibility of the erythrocytes.

                  TABLE I                                                          ______________________________________                                                            ED.sub.50 of the                                            Example No.        inhibition (mol/l)                                          ______________________________________                                          3                 5 × 10.sup.-6                                         13                 5 × 10.sup.-6                                         21                 5 × 10.sup.-6                                         27                    10.sup.-6.                                               ______________________________________                                    

b) Antihaemolytic action of erythrocytes

Normal erythrocytes become haemolytic under high shearing stresses. The haemolysis of calcium-laden cells is particularly pronounced. This measure of mechanical stability is used for substance characterization. The measured quantity is the concentration of free haemoglobin in the medium.

                  TABLE II                                                         ______________________________________                                                           ED.sub.50 of the                                                               antihaemolytic action                                        Example No.       (mol/l)                                                      ______________________________________                                          2                   10.sup.-7                                                 13                5 × 10.sup.-7                                          15                5 × 10.sup.-6                                          21                5 × 10.sup.-7                                          22                5 × 10.sup.-7                                          26                3 × 10.sup.-8                                          27                 5 × 10.sup.-8.                                        ______________________________________                                    

c) Filtration of erythrocytes

Filtration of erythrocytes through 5 μm sieve pores is an established method for the determination of the deformability of erythrocytes. The cells are sheared in normal buffer for 30 min so that the calcium concentration increases intracellularly and the flexibility is reduced.

                  TABLE III                                                        ______________________________________                                                  ED.sub.50 improvement in the flexibility                              Ex. No.  compared to damage to control (mol/l)                                 ______________________________________                                          1       5 × 10.sup.-6                                                    3       5 × 10.sup.-6                                                   26       5 × 10.sup.-6                                                   28        5 × 10.sup.-6.                                                 ______________________________________                                    

d) Viscosity in glass capillaries

The biophysical interactions of erythrocytes relevant to the circulation can be investigated in glass capillaries (diameter 20-30 μm). The resulting viscosity depends on the condition of the cells. In the case of calcium loading, the viscosity increases. The percentage improvement in the viscosity relative to the damaged but untreated control is given at 0.7 Pa. The test dose is 10⁻⁸ g/ml.

                  TABLE IV                                                         ______________________________________                                         Example No.    Effect (%)                                                      ______________________________________                                          3             143                                                             13             120                                                             14             206                                                             15              75                                                             17              62                                                             18             208                                                             24             226                                                             ______________________________________                                    

II) Leukocyte function

The microcirculation can be directly observed in the hamster cheek pouch model. Measured quantities are leukocyte adhesion and also vessel diameter and erythrocyte velocity. The adhesion was quantified under ischaemic and non-ischaemic experimental conditions. Under non-ischaemic conditions, the adhesion is quantified in the area of small venules, under ischaemic conditions (10 min circulation stop) the adhesion is quantified in small arterioles. The results of the control experiments are given relative to 100%. 0.1 mg/kg i.v. is in each case chosen as the test dose, the results are decreases in % of the control.

                  TABLE V                                                          ______________________________________                                                     Non-ischaemic                                                                               Ischaemic                                             Example No. control = 100%                                                                              control = 100%                                        ______________________________________                                         3           63%          31%                                                   6           50%          56%                                                   9           70%          36%                                                   18          54%          32%                                                   19          61%          34%                                                   ______________________________________                                    

III) Blood pressure

The clinical state of knowledge shows that anti-ischaemic actions of dihydropyridines are frequently masked by vasodilatation. It was therefore the aim to find blood pressure-inactive DHPs (i.e. difference between haemorheological action and blood pressure-reducing action ≧10). The following table shows the doses at which a blood pressure reduction occurs in the case of p.o. administration (SH rats) or i.v. administration (anaesthetized Wistar rats).

                  TABLE VI                                                         ______________________________________                                         Example No.   p.o. (mg/kg)                                                                              i.v. (mg/kg)                                          ______________________________________                                         3             >30        >10                                                   6             >30        >10                                                   9             >30        >10                                                   18            >30        >10                                                   19            >100       >10                                                   ______________________________________                                    

The table shows that, in comparison to model II, the difference between the therapeutic action and blood pressure action (i.v.) is at least 100.

The new active compounds can be converted in a known manner into the customary formulations, such as tablets, coated tablets, pills, granules, aerosols, syrups, emulsions, suspensions and solutions, using inert, non-toxic, pharmaceutically suitable excipients or solvents. In this connection, the therapeutically active compound should in each case be present in a concentration of about 0.5 to 90% by weight of the total mixture, i.e. in amounts which are sufficient in order to achieve the dosage range indicated.

The formulations are prepared, for example, by extending the active compounds with solvents and/or excipients, if appropriate using emulsifiers and/or dispersants, where, for example, in the case of the use of water as a diluent, organic solvents can optionally be used as auxiliary solvents.

Administration is carried out in a customary manner, preferably orally or parenterally, in particular perlingually or intravenously.

In the case of parenteral use, solutions of the active compounds using suitable liquid excipient materials can be employed.

In general it has proved advantageous on intravenous administration to administer amounts of about 0.001 to 1 mg/kg, preferably about 0.01 to 0.5 mg/kg of body weight to achieve effective results, and on oral administration the dosage is about 0.01 to 20 mg/kg, preferably 0.1 to 10 mg/kg of body weight.

In spite of this, it may be necessary to deviate from the amounts mentioned, in particular depending on the body weight or the type of administration route, on individual behavior towards the medicament, the nature of its formulation and the point in time or interval at which administration takes place. Thus, in some cases it may be sufficient to manage with less than the above-mentioned minimum amount, while in other cases the upper limit mentioned must be exceeded. In the case of the administration of larger amounts, it may be advisable to divide these into several individual doses over the course of the day.

PREPARATION EXAMPLES Example 1

Diethyl 1,2,6-trimethyl-4-(4-fluorophenyl)-1,4-dihydropyridine-3,5-dicarboxylate ##STR9##

2.78 g (0,008 mol) of diethyl 2,6-dimethyl-4-(4-fluorophenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate are dissolved in 25 ml of 1,2-dimethoxyethane, and 0.30 g (0.01 mol) of 80% strength sodium hydride and, after 30 min, 1.43 g (0.01 mol) of methyl iodide are added. The mixture is stirred at room temperature for 3 hours, neutralized with dilute hydrochloric acid and evaporated in vacuo. The residue is purified by chromatography on silica gel (methylene chloride).

Yield: 1.85 g (63.9% of theory).

Melting point: 90°-92° C.

Example 2

Dimethyl 4-(3-fluorophenyl)-1,2,6-trimethyl-1,4-dihydropyridine-3,5-dicarboxylate ##STR10##

A mixture of 3.84 g (0.03 mol) of 3-fluorobenzaldehyde, 7.04 g (0.06 mol) of methyl acetoacetate and 2.07 g (0.03 mol) of methylamine hydrochloride in 20 ml of pyridine is stirred under reflux for 5 hours. After removing the pyridine by distillation, the mixture is partitioned between water and methylene chloride, and the organic phase is washed with water, dried over sodium sulphate and evaporated. The residue is recrystallized from methanol.

Melting point: 117°-118° C.

Yield: 6.14 g (61.4% of theory)

Example 3

Dimethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate ##STR11##

A mixture of 5.22 g (0.03 mol) of 4-trifluoromethylbenzaldehyde, 7.04 g (0.06 mol) of methyl acetoacetate and 2.07 g (0.03 mol) of methylamine hydrochloride in 20 ml of pyridine is stirred under reflux for 5 hours. After removing the pyridine by distillation, the mixture is partitioned between water and methylene chloride, and the organic phase is washed with water, dried over sodium sulphate and evaporated. The residue is recrystallized from methanol.

Melting point: 154°-155° C.

Yield: 7.88 g (68.5% of theory)

The examples shown in Tables 1 and 2 were prepared in analogy to the procedure of Example 3.

                                      TABLE 1                                      __________________________________________________________________________      ##STR12##                                                                     Example No.                                                                           R.sup.1'  R.sup.4'                                                                           R.sup.5'                                                                           m.p. °C.                                                                     Yield (% of theory)                              __________________________________________________________________________             ##STR13##                                                                               --C.sub.2 H.sub.5                                                                  --C.sub.2 H.sub.5                                                                  90-92                                                                               63.9                                             __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________      ##STR14##                                                                     Ex. No.                                                                             R.sup.1'                                                                          R.sup.3'                                                                         R.sup.4'  R.sup.5'                                                                           m.p. °C.                                                                      Yield (% of theory)                              __________________________________________________________________________     5    H  CN                                                                               --C.sub.3 H.sub.7                                                                        --C.sub.3 H.sub.7                                                                  Oil  19.4                                              6    NO.sub.2                                                                          H --C.sub.4 H.sub.9                                                                        --C.sub.4 H.sub.9                                                                  81-84                                                                               62.7                                              7    CF.sub.3                                                                          H --C.sub.3 H.sub.7                                                                        --CH.sub.3                                                                         76-78                                                  8    CF.sub.3                                                                          H --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         86-88                                                  9    CF.sub.3                                                                          H                                                                                 ##STR15##                                                                               --CH.sub.3                                                                         54-57                                                  10   CF.sub.3                                                                          H --(CH.sub.2).sub.2 --OCH.sub.3                                                           --CH.sub.3                                                                         71-73                                                  __________________________________________________________________________

Example 11

Dipropyl 4-(4-bromophenyl)-1,2,6-trimethyl-1,4-dihydropyridine-3,5-dicarboxylate ##STR16##

A solution of 6.22 g (0.02 mol) of propyl 2-(4-bromobenzylidene)acetoacetate and 3.14 g (0.02 mol) of propyl 3-methylamino-crotonate in 25 ml of 2-butanol is stirred under reflux for 10 hours. The mixture is then concentrated in vacuo, and the precipitate formed in the cold is filtered off with suction. After recrystallization from propanol, 5.32 g (59.1% of theory) of melting point 97°-99° C. are obtained.

The compounds shown in Table 3 can be prepared analogously to Example 11.

                                      TABLE 3                                      __________________________________________________________________________      ##STR17##                                                                     Ex. No.                                                                             R.sup.1'                                                                            R.sup.2'                                                                           R.sup.4'   R.sup.5'                                                                              R.sup.6'                                                                           m.p. °C.                                                                     Yield (% of theory                    __________________________________________________________________________     12   H    --CH.sub.3                                                                         --C.sub.3 H.sub.7                                                                         --C.sub.3 H.sub.7                                                                     --CH.sub.3                                                                         67-68                                                                               23.3                                  13   --Br H   --CH.sub.3 --CH.sub.3                                                                            --CH.sub.3                                                                         163-167                                                                             59.5                                  14   --Br H   --C.sub.4 H.sub.9                                                                         --C.sub.4 H.sub.9                                                                     --CH.sub.3                                                                         66-68                                                                               36.5                                  15   --CN H   --C.sub.3 H.sub.7                                                                         --C.sub.3 H.sub.7                                                                     --CH.sub.3                                                                         116-119                                                                             45.7                                  16   H    --CF.sub.3                                                                         --C.sub.2 H.sub.5                                                                         -- C.sub.2 H.sub.5                                                                     ##STR18##                                                                         112-114                                                                             22.4                                  17   --CF.sub.3                                                                          H   --CH.sub.3 --CH.sub.3                                                                            --C.sub.2 H.sub.5                                                                  119-129                                                                             15.5                                  18   --CF.sub.3                                                                          H   --CH.sub.3 --CH.sub.3                                                                             ##STR19##                                                                         137-138                                                                             15.6                                  19   --CF.sub.3                                                                          H   --C.sub.2 H.sub.5                                                                         --C.sub.2 H.sub.5                                                                      ##STR20##                                                                         111-113                                                                             15.5                                  20   --CF.sub.3                                                                          H   --CH(CH.sub.3).sub.2                                                                      --CH(CH.sub.3).sub.2                                                                  --CH.sub.3                                                                         106-108                                                                             49.1                                  21   --CH.sub.3                                                                          --NO.sub.2                                                                         --CH.sub.3 --CH.sub.3                                                                            --CH.sub.3                                                                         116-118                                                                             66.1                                  22   --CH.sub.3                                                                          --NO.sub.2                                                                         --C.sub.2 H.sub.5                                                                         --C.sub.2 H.sub.5                                                                     --CH.sub.3                                                                         97-98                                                                               60.1                                  23   --CH.sub.3                                                                          --NO.sub.2                                                                         --C.sub.3 H.sub.7                                                                         --C.sub.3 H.sub.7                                                                     --CH.sub.3                                                                         94-96                                                                               41.3                                  24   --CH.sub.3                                                                          --NO.sub.2                                                                         --C.sub.4 H.sub.9                                                                         --C.sub.4 H.sub.9                                                                     --CH.sub.3                                                                         89-90                                                                               45.4                                  25   --NO.sub.2                                                                          Cl  --C.sub.2 H.sub.5                                                                         --C.sub.2 H.sub.5                                                                     --CH.sub.3                                                                         128-130                                                                             60.1                                  26   --Cl --CF.sub.3                                                                         --CH.sub.3 --CH.sub.3                                                                            --CH.sub.3                                                                         122-124                                                                             63.8                                  27   --CH.sub.3                                                                          --CF.sub.3                                                                         --CH.sub.3 --CH.sub.3                                                                            --CH.sub.3                                                                         103-105                                                                              4.83                                 28   --NO.sub.2                                                                          --OH                                                                               --CH.sub.3 --CH.sub.3                                                                            --CH.sub.3                                                                         187-189                                                                             62.6                                  29   --OCF.sub.3                                                                         H   --CH.sub.3 --CH.sub.3                                                                             ##STR21##                                                                         77-78                                                                               13.2                                  30   --OCF.sub.3                                                                         H   --C.sub.2 H.sub.5                                                                         --C.sub.2 H.sub.5                                                                      ##STR22##                                                                         108-109                                                                             18.5                                  31   --CF.sub.3                                                                          H   --CH.sub.2 --CH.sub.2 --OCH.sub.3                                                         --CH(CH.sub.3).sub.2                                                                  --CH.sub.3                                                                         Oil  74.3                                  .sup. 31a                                                                           (+)-Enantiomer [α].sub.589.sup.20 10.3 (C = 1 in CHCl.sub.3)        .sup. 31b                                                                           (-)-Enantiomer [α].sub.589.sup.20 -10.1 (C =  1 in                  __________________________________________________________________________          CHCl.sub.3)                                                          

Example 32

Diethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate ##STR23##

0.55 ml (5 mmol) of titanium tetrachloride, then 1 ml (10 mmol) of piperidine are added under nitrogen protection to 20 ml of toluene and the mixture is stirred for 5 min. After the dropwise addition of 2.9 g (20 mmol) of methyl 3-methylaminocrotonate, 1.36 ml (10 mmol) of 4-trifluoromethylphenylbenzaldehyde are added and the mixture is stirred at room temperature for 3 hours. For working up, 100 ml of 5% strength hydrochloric acid are added and the organic phase is taken up with ethyl acetate, and the ethyl acetate solution is washed successively with 5% hydrochloric acid and with sodium bicarbonate solution. After drying the ethyl acetate solution over sodium sulphate, evaporating and stirring the residue in n-heptane, 1.7 g (41.4% of theory) are obtained.

Melting point: 98° C.

Example 33

Methyl ethyl 1-cyclopropyl-2,6-dimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate ##STR24##

3.6 g (0.039 mol) of cyclopropylamine hydrochloride are added to a solution of 3.9 g (0.03 mol) of ethyl acetoacetate and 8.16 g (0.03 mol) of methyl 2-(4-trifluoromethylbenzylidene)acetoacetate in 50 ml of pyridine and the mixture is heated under reflux for 5 hours. The reaction product is concentrated in vacuo, the residue is taken up in methylene chloride and water, the aqueous phase is separated off, and the methylene chloride solution is dried over sodium sulphate and evaporated. The residue is purified by chromatography on silica gel using methylene chloride as the solvent. After dissolving and crystallizing the product from n-heptane, 2.2 g

(17.3% of theory) are obtained.

Melting point: 110° C.

The compounds shown in Table 4 can be prepared in analogy to the procedure of Examples 32 and 33.

                  TABLE 4                                                          ______________________________________                                          ##STR25##                                                                     Ex. No.                                                                               R.sup.1' R.sup.4'    R.sup.5' m.p. °C.                           ______________________________________                                         34     --CF.sub.3                                                                              --C.sub.4 H.sub.9                                                                          --C.sub.3 H.sub.7                                                                       62                                        35     --CF.sub.3                                                                              --(CH.sub.2).sub.2 OCH.sub.3                                                               --C.sub.3 H.sub.7                                                                       Oil                                       36     --F      --CH.sub.3  --CH.sub.3                                                                              140                                       37     --F      --C.sub.2 H.sub.5                                                                          --C.sub.2 H.sub.5                                                                       79                                        38     --CF.sub.3                                                                              --C.sub.4 H.sub.9                                                                          --CH.sub.3                                                                              Oil                                       39     --CF.sub.3                                                                              --C.sub.3 H.sub.7                                                                          --C.sub.2 H.sub.5                                                                       55-57                                     40     --CF.sub.3                                                                              --C.sub.4 H.sub.9                                                                          --C.sub.2 H.sub.5                                                                       55-60                                     41     --CF.sub.3                                                                              --C.sub.2 H.sub.5                                                                          --CH(CH.sub.3).sub.2                                                                    96                                        ______________________________________                                    

The examples shown in Table 5 were prepared in analogy to the procedures of Examples 1, 3 and 11.

                                      TABLE 5                                      __________________________________________________________________________      ##STR26##                                                                     Example                                   Yield                                No.  R.sup.1'                                                                            R.sup.2'                                                                           R.sup.4' R.sup.5'  R.sup.6'                                                                           m.p. °C.                                                                     (% of theory)                        __________________________________________________________________________     42   --CF.sub.3                                                                          H   --CH.sub.3                                                                              --C.sub.2 H.sub.5                                                                        --CH.sub.3                                                                         116-118                                                                             78                                   43   --F  H   --CH.sub.3                                                                              --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         92-94                                                                               73                                   44   --F  H   C.sub.2 H.sub.5                                                                         --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         Oil  73                                   45   --CF.sub.3                                                                          H   --(CH.sub.2).sub.2 OCH.sub.3                                                            --C.sub.2 H.sub.5                                                                        --CH.sub.3                                                                         56-57                                                                               57                                   46   --CF.sub.3                                                                          H   --(CH.sub.2).sub.2 OCH.sub.3                                                            CH.sub.2 --CH(CH.sub.3).sub.2                                                            --CH.sub.3                                                                         55-60                                                                               68                                   47   --F  --CF.sub.3                                                                         --CH.sub.3                                                                              --CH.sub.3                                                                               --CH.sub.3                                                                         133  59                                   48   --F  --CF.sub.3                                                                         --C.sub.2 H.sub.5                                                                       --C.sub.2 H.sub.5                                                                         ##STR27##                                                                          61  19                                   49   --CF.sub.3                                                                          H   --CH.sub.3                                                                              --CH.sub.2 --CH(CH.sub.3).sub.2                                                          --CH.sub.3                                                                          68  58                                   50   --CF.sub.3                                                                          H   --C.sub.2 H.sub.5                                                                       --CH.sub.2 --CH(CH.sub.3).sub.2                                                          --CH.sub.3                                                                          63  75                                   51   --F  --CF.sub.3                                                                         --CH.sub.3                                                                              --CH.sub.3                                                                                ##STR28##                                                                         118  27                                   52   --F  --CF.sub.3                                                                         --C.sub.2 H.sub.5                                                                       --C.sub.2 H.sub.5                                                                        --CH.sub.3                                                                          83  63                                   53   --OCF.sub.3                                                                         H   --(CH.sub.2).sub.2 OCH.sub.3                                                            CH.sub.2 --CH(CH.sub.3).sub.2                                                            --CH.sub.3                                                                          62  21                                   54   --OCF.sub.3                                                                         H   --C.sub.2 H.sub.5                                                                       -- CH.sub.2 CH(CH.sub.3).sub.2                                                           --CH.sub.3                                                                          73  19                                   55   --CF.sub.3                                                                          H   --(CH.sub.2).sub.2 OCH.sub.3                                                            --CH.sub.2 --CH(CH.sub.3).sub.2                                                          --CH.sub.3                                                                         Oil  45                                                                    (-) enant.                                                                     α.sub.589.sup.20 : -11.1                                                 (CHCl.sub.3), c. 0.85                         56   --CN H   --CH.sub.3                                                                              --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         122  50                                   57   --CF.sub.3                                                                          H   --CH.sub.2 CH(CH.sub.3).sub.2                                                           --CH.sub.2 CH(CH.sub.3).sub.2                                                            --CH.sub.3                                                                          68  45                                   58   --CN H   --C.sub.2 H.sub.5                                                                       --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         106-107                                                                             50                                   59   --CF.sub.3                                                                          H   --CH.sub.2 CH(CH.sub.3).sub.2                                                           --CH.sub.2 CH(CH.sub.3).sub.2                                                             ##STR29##                                                                          92  11                                   60   --F  --CF.sub.3                                                                         --(CH.sub.2).sub.2 OCH.sub.3                                                            --CH(CH.sub.3).sub.2                                                                     --CH.sub.3                                                                         82-83                                                                               25                                   61   --CF.sub.3                                                                          H   --C.sub.6 H.sub.13                                                                      --CH.sub.3                                                                               --CH.sub.3                                                                         64-65                                                                               36                                   62   --CF.sub.3                                                                          H   --C.sub.4 H.sub.9                                                                       --CH.sub.3                                                                               --CH.sub.3                                                                         71-73                                                                               28                                   63   --CF.sub.3                                                                          H   --C.sub.5 H.sub.11                                                                      --CH.sub.3                                                                               --CH.sub.3                                                                         75-77                                                                               13                                   64   --Cl H   --CH.sub.3                                                                              --CH.sub.3                                                                               --C.sub.2 H.sub.5                                                                  143  21                                   65   --Cl H   --CH.sub.3                                                                              --CH.sub.3                                                                               --CH.sub.3                                                                         181  19                                   __________________________________________________________________________ 

We claim:
 1. A method of treating a patient exhibiting an acute or chronic ischaemic disorder that is associated with disorders of microcirculation, without lowering or increasing blood pressure, said method comprising administering to said patient an amount effective therefor of an N-alkylated 1,4-dihydropyridine of the formula: ##STR30## in which R¹ represents hydrogen, nitro, trifluoromethyl or fluorine,R² represents hydrogen, fluorine or trifluoromethyl, R⁴ and R⁵ are identical or different and represent straight-chain or branched alkyl having up to 8 carbon atoms, which is optionally substituted by alkoxy having up to 4 carbon atoms, and R⁶ represents straight-chain or branched alkyl having up to 10 carbon atoms or cycloalkyl having 3 to 7 carbon atoms.
 2. The method according to claim 1, in whichR⁴ and R⁵ are identical or different and represent straight-chain or branched alkyl having up to 6 carbon atoms, which is optionally substituted by methoxy, and R₆ represents straight-chain or branched alkyl having up to 8 carbon atoms, or cyclopropyl.
 3. The method according to claim 1, wherein the patient has an an acute or chronic ischaemic disorder.
 4. The method according to claim 1, wherein such compound is:dimethyl 1,2,6-trimethyl-4-(4-trifluoromethylphenyl)-1,4-dihydro-pyridine-3,5-dicarboxylate, diethyl 4-(3-trifluoromethylphenyl)-1-cyclopropyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, dimethyl 4-(4-trifluoromethylphenyl)-1-ethyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, dimethyl 4-(4-trifluoromethylphenyl)-1-cyclopropyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, or diethyl 4-(4-trifluoromethylphenyl)-1-cyclopropyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate. 